1. Field
Methods and apparatuses consistent with exemplary embodiments relate to an optically addressable spatial light modulator (OASLM)-based holographic display.
2. Description of the Related Art
In recent years, there has been an increasing demand for three-dimensional (3D) image display devices capable of more realistically and effectively displaying an image in various fields such as movies, games, advertisements, medical images, education, or military. Thus, various techniques for displaying a 3D image have been suggested, and various 3D image display devices have been already commercialized. 3D image display devices that are currently commercialized operate based on the principle of binocular parallax caused by the distance between the left and right eyes. Such 3D image display devices provide an image for the left eye and an image for the right eye, which have different viewpoints with respect to the left eye and the right eye of a viewer, so that the viewer may perceive a 3D effect. 3D image display devices are classified into glasses type 3D image display devices requiring use of special glasses and non-glasses type 3D image display devices not requiring use of glasses.
In the case of stereoscopy type display devices using the principle of binocular parallax, severe eyestrain may occur, and only two viewpoints of an image: for the left eye and an image for the right eye are provided, and thus, a viewpoint variation according to the movement of a viewer may not be accounted for. Therefore, there is a limitation in providing a natural 3D effect. In order to more naturally display a stereoscopic image by addressing this limitation, a holographic display technology has been investigated.
In the holographic display technology, when a hologram having recorded therein an interference fringe, which is obtained by interference between a laser beam reflected from an original object and a reference beam, is irradiated with the reference beam and then the reference beam is diffracted, an image of the original object is reproduced. A holographic display technology that is currently used provides a computer generated hologram (CGH) as an electrical signal to a spatial light modulator rather than obtaining a hologram by directly exposing an original object to light. A 3D image may be generated by the spatial light modulator diffracting a reference beam in response to a CGH signal to be input.
In such a holographic display technology, in order for a reproduced 3D image to have a sufficient resolution and viewing angle (that is, in order for a reproduced 3D image to have a large space bandwidth), the performance of a spatial light modulator is important. In a general electrically addressable spatial light modulator (EASLM), a driving circuit and a wiring line are disposed in each pixel, and thus, there is a limitation in reducing the size of the pixel. Thus, a holographic display using an optically addressable spatial light modulator (OASLM) has been suggested. Since an OASLM includes a photoelectric conversion layer that is disposed on a surface on which a recording beam is incident, the OASLM may selectively turn on only pixels of a region on which the recording beam is incident. As an OASLM does not require an additional driving circuit and wiring line, the resolution requirements may be improved.